Pressurized fluid jet technology is well known and is used today in various applications, such as for eroding, debriding as well as removing contaminants from metal surfaces. For example, high pressure fluid jet technology has been used to effectively remove loose paint, rust and other gross contaminants from surfaces. It has also effectively been used to remove water soluble salts that are often found deep within the microscopic pits of a substrate. In many cases, water alone is used as the fluid, particularly when the contaminant is not strongly adhered to the surface. In other cases, a surfactant is needed, particularly when the contaminant is a hydrocarbon material. In still other cases it is necessary to use an abrasive material, such as a particulate material of suitable particle size and hardness, to remove strongly adhered contaminants and to leave a clean surface.
The equipment used to create the pressurized fluid stream will vary depending on the desired delivery pressure of the fluid. For example, low pressure (about 500 to about 1,500 psi) and intermediate pressure (about 2,000 to about 3,500 psi) units are often portable and are typically used for cleaning equipment, pavements, etc. They are sometimes used in combination with water heaters and surfactant systems since chemical and/or thermal energy inputs are frequently required to augment these systems. The high pressure (about 5,000 to about 15,000 psi) and ultra high pressure (15,000 to 35,000 psi) units are often truck mounted, or are occasionally stationary where objects are brought to be cleaned. The high pressure and, particularly ultra high pressure, units are more hazardous to use since they operate at dangerously high hydraulic energy levels. Further, transportation and disposal costs for the large quantities of liquid wastes generated in a typical hdyrojet cleaning application can be substantial. Water jetting, particularly at pressures greater than about 5,000 psi, is considered to be an extremely dangerous operation. Each year, a number of deaths and serious injuries result either directly from lacerations or from infections due to “hyrodermic” injections of dirty plant water. Conversely, at lower, safer pressures, the process is simply not effective. Other disadvantages include poor visibility, relatively high equipment and operating costs, operator fatigue brought on by working with such high thrust devices, and high water consumption.
In conventional pressurized fluid technology the primary, or carrier fluid, of the pressurized fluid stream is accelerated at the desired velocity and an additive, be it an abrasive, or a liquid such as a surfactant, is entrained into the carrier stream by the vacuum created by the flowing carrier stream. Such a system has the disadvantage in that substantially higher pressures are required for the carrier fluid stream than the desired fluid delivery stream pressure. Also, mixing of an additive is often inadequate for certain uses. Therefore, there exists a need in the art for more effective pressurized fluid spraying apparatus.